LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

97 Z28 Intake Air Temperature Question

Old 04-21-2019, 07:48 PM
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Question 97 Z28 Intake Air Temperature Question

Hello All, My Z28 has started stumbling on longer drives, ie 15-20+ minute drives, I plugged up my live scanner and quickly went through all the live diagnostics and noticed that the IAT temp was 116 degrees. I drove it for a second to see if it would go up or down and it stayed around 111-116. Iím curious if any of you have seen what your Idle Air Temp registers after your cars have been running for awhile,(15 minutes plus).
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Old 04-21-2019, 10:29 PM
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re: 97 Z28 Intake Air Temperature Question

The IAT sensor tends to heat soak from under hood temps, indicating higher than actual ambient air temp. On a hot summer day, A/C on, sitting in stop & go traffic, I've seen the IAT reach 140įF. I relocated the sensor to the end cap on the filter of my cold air intake and it read closer to ambient.

I've also reviewed 100’s of PCM data logs for people, and the problem shows up at idle and low speeds, but temp typically tends to drop as the engine RPM and vehicle MPH go up. I would expect yours to drop like that, but I have no idea what the ambient air temp was where you were driving, or how fast you were going.

Unless you have a 1993 running speed-density (no MAF sensor), or if the MAF sensor fails and the 94-97 PCM defaults to speed-density, IAT is not all that important. I did feel that when I got the 140į reading, the idle seemed rougher and the power off idle seemed down slightly. My thought was the PCM was pulling a bit of timing to prevent detonation, but I was never able to confirm that.
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Old 04-21-2019, 10:49 PM
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re: 97 Z28 Intake Air Temperature Question

Thank you Injuneer, that’s what I needed to know.
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Old 04-22-2019, 08:08 AM
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re: 97 Z28 Intake Air Temperature Question

PS: It’s INLET (or INTAKE) Air Temperature.

Last edited by Injuneer; 04-22-2019 at 08:11 AM.
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Old 04-22-2019, 11:24 AM
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re: 97 Z28 Intake Air Temperature Question

When iíve been playing with my Ď95z iíve found if i stop the car and restart once warm, itíll run a few points leaner then richens back up slowly as the iat starts to drop. Iím not sure why it should affect the tune that way but playing with the tables doesnít seem to make much difference either.
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Old 04-22-2019, 06:18 PM
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re: 97 Z28 Intake Air Temperature Question

Originally Posted by Injuneer View Post
PS: Itís INLET (or INTAKE) Air Temperature.
Thanks for the correction, I guess I was thinking of an IAC
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